Neil,
Actually, from my diagnostics, its more of the second PC doing read caching than write caching. ie Upon PC A saving a record, if PC B was already in the form before PC A saved the record, PC B will never get to see PC A's record. However, if PC B were to exit the form and come in again, PC B will be able to see PC A's record.
Its like PC B is totally not refreshing its caches after it goes into a form.
Yau